Liquid crystal molecules have birefringence, and have refractive index anisotropy, or a property that a refractive index varies depending on a passing direction of light. A liquid crystal display is a display unit that uses the liquid crystal molecules as an optical switch, and displays an image by electrically operating transmission and blocking of light, with utilization of a change in the refractive index due to a change in molecular sequence (alignment) of the liquid crystal molecules caused by application of an electric field.
In the liquid crystal display, polarized light is used as the light to pass therethrough. Out of the light passing through a liquid crystal layer having a certain thickness, obliquely-advancing light has a long passage distance in the liquid crystal layer and is readily affected by the change in the refractive index due to the liquid crystal molecules, which may result in, for example, a significant change in a vibration axis of the polarized light. This change in the vibration axis of the polarized light lowers a function as the optical switch (blocking/transmission) and display characteristics (in particular, contrast) of the liquid crystal molecules. In particular, influence thereof is noticeable as viewed in an oblique direction.
For the liquid crystal display, various liquid crystal modes have been developed to reduce the anisotropy of the refractive index due to the liquid crystal molecules. In each of the various liquid crystal modes, an inner structure of a display panel is devised. But effects thereof are far from sufficient. For example, in an MVA (multi-domain vertical alignment) mode, a plurality of regions that vary in alignment direction of liquid crystal molecules may be formed (alignment division thereof is performed) in one pixel unit. The refractive index anisotropy may be reduced by averagely neutralizing the alignment direction. But an effect of improving a viewing angle characteristic in the oblique direction may be low. In an IPS (in-plane switching) mode, a change in optical characteristics due to a viewing angle is reduced by constantly rotating liquid crystal molecules in a plane with respect to a substrate. But an effect thereof is noticeably low in a certain direction. In addition, in recent years, the number of pixels has increased due to upsizing and higher definition of display units, and greater complexity of the inner structure has caused an increase in costs of patterning and other processes.
Therefore, a method of improving the viewing angle characteristic in an outside of the display panel has been developed. For example, Patent Literature 1 discloses a liquid crystal display in which a lens sheet is disposed on a front face of a liquid crystal panel. In the lens sheet, columnar lenses or prismatic prism lenses are arranged in one direction.